Electrostatographic or xerographic printing devices, such as copiers or digital "laser printers," are well known. In many types of apparatus, a key area from a reliability standpoint is the zone between the charge-retentive member, such as a photoreceptor, and the fuser. The sheet that receives an image from the photoreceptor in a transfer step must be pulled from the photoreceptor (which is typically in the form of a rotating drum or belt) and, as smoothly as possible, directed to a fuser, which typically comprises two rollers forming a nip therebetween. The length of the gap between the photoreceptor and the fuser is crucial when the machine is handling short sheets as the photoreceptor may not ensure continuous drive to deliver the sheet to the fuser, causing a paper jam. If the sheet is caused to jam very close to the fuser, heat from the fuser is liable to create a dangerous situation. Further, because the toner image on the sheet as it passes from the photoreceptor to the fuser is only loosely attached to the sheet, any irregularities in the paper feeding between the photoreceptor and the fuser are likely to cause unacceptable smearing of the image.
In many designs of copiers or printers, particularly of the high-speed variety, the preferred device for moving a sheet from the photoreceptor to the fuser is a vacuum transport. A typical design of a vacuum transport is shown in FIG. 4. As shown in the Figure, the vacuum transport generally indicated as 100 is disposed within a copier or printer between a photoreceptor 102 and the fuser rolls 104. Vacuum transport 100 itself typically comprises a belt 110 which is entrained about two rollers 112, 114. This belt 110 typically defines a number of small holes therein (not shown). Disposed inside the belt 110 is a vacuum chamber 116. The vacuum chamber 116 is an actuated by a motor (not shown) and thereby draws air through the holes in belt 110 particularly in the area where a sheet moving in a process direction in is passing over the belt 110. In this way, vacuum chamber 116 holds a sheet against the outer surface of belt 110, while belt 110 moves that sheet from photoreceptor 100 toward the nip of fuser rolls 104.
While the vacuum transport of the general design shown in the Figure has long been proven to be effective, it suffers from various impracticalities. For instance, transport 100 tends to be heavy and expensive, and the belt 110 may require replacement over the life of the machine. The large size of the vacuum transport tends to preclude its use in compact printers and copiers. The present invention is directed toward a small, low-cost, yet effective vacuum transport.